Rigid recording disk cartridges having a circular, floppy, magnetic or optical disk rotatably mounted within a disk cartridge case are well known. The cartridge is mountable in a disk drive apparatus to rotate and access the recording disk by a magnetic or optical recording head for recording or reproducing information. The disk cartridge includes a rotatable magnetic or optical disk, a cartridge case for housing the disk having a central axis and a front wall, and a U-shaped shutter slidably disposed on the front wall of the case.
Upper and lower walls mate to form the outer dimensions of the cartridge case. A drive shaft opening is formed through a central portion of the lower wall to receive a drive shaft to rotate the magnetic disk within the cartridge case. A head access opening is formed in the upper and lower walls between the central axis and the front wall to access the magnetic disk. The head access opening is opened and closed by the shutter which slides between open and closed positions. A spring biases the shutter in the closed position to cover and close the head access opening. The spring is connected to the shutter with a shutter spring hook formed on the shutter. When the cartridge is inserted into the disk drive, the shutter is moved to the open position by the disk drive to provide access to the disk. The shutter may also include one or more tabs which ride in a slot in the wall of the cartridge to guide the shutter.
U.S. Pat. Nos. 4,853,817 to Mizuta et al., 4,851,948 to Kato et al., 4,839,953 to Mizuta, and 4,785,369 to Ommori et al. are examples of magnetic disk cartridges in which the shutter spring is connected to the shutter with a shutter spring hook formed on the shutter. This hook is shown, for example in FIG. 3 of the '817 patent, FIG. 4 of the '953 patent, FIGS. 9 and 18 of the '948 patent, and FIGS. 1-4 of the '369 patent. Typically, these hooks are mounted on the base of the U-shaped shutter and are formed in a relatively complex molding operation. This operation requires that an additional opening or window be formed in one of the arms of the U as a slide is inserted into the mold to form the rounded or upturned undercut portion of the hook. This increases the mold costs and mold maintenance costs, and decreases the aesthetics of the shutter. Overland et al., U.S. Pat. No. 5,021,913 discloses a shutter made by stamping or punching metal which also uses a shutter hook. As shown in FIG. 5, this hook requires an opening be formed in the base of the shutter. The openings made to accommodate the shutter hook in these patents detracts from the aesthetic appearance of the shutter. Moreover, during assembly, the spring can miss and slide around the hook or pop out of the window adjacent the hook.
The '913 patent also discloses a shutter hook which extends outwardly from the shutter both during manufacture and when the shutter is assembled onto the cartridge. This shutter is used with an elongate compression spring as shown in FIG. 10.
Furthermore, systems for molding these shutters require four shutoffs on the slide action of the mold. One forms the large shutter window, another forms the shutter groove tab, a third forms the second shutter groove tab, and the fourth forms the spring hook. Additionally, standard yield at the spring station with the spring hook design is only approximately 90%.
There is a need for a shutter spring stop which overcomes these problems with known designs.